10 June 2003

The Low in the deep tropics continues to organize as it heads west...

Although still not a Tropical Depression, the 1009mb Low has a very
obvious mid-level circulation and convection has maintained the cloud
tops at -70C or colder.  It's presently at about 10N 39W and tracking
WNW at 15-20 kts.  

The SSTs are marginal at 26C, and this will not improve unless it makes
it to west of 50W where the ocean is warmer at higher latitudes. 
However, it remains in a very favorable low-shear environment.

This is quite early in the season for a Cape Verde storm to develop.  In
recent memory, there was Bertha '96 who formed on July 5 at 34W.  Then
going all the way back to 1976, Ana formed on June 19 at 45W.  I didn't
search beyond 35 years ago, but the point is, it would be very rare if
this developed to a named storm!

As an aside, the disturbance is embedded in a SAL, or Saharan Air
Layer.  This is still a very active area of research in the tropical
meteorology community, but basically, it's a dry layer of air, traceable
by fine dust and sand particles, that originates from the Sahara Desert
and blows out over the tropical Atlantic with the easterlies.  The dry
layer of air is unhealthy for convection, and sometimes you'll notice a
diminished intensity in convection despite amply warm SSTs... look for
this dust as a possible culprit!  Today, the SAL reaches to the Lesser
Antilles.  On a technical note for those who are curious, you can
typically see the SAL much better in the morning's visible imagery... it
appears to almost vanish by afternoon/evening.  This is the effect of
forward scattering.  You can see an example of the SAL at
which is from today at 1145Z.

Please visit my tropical Atlantic headquarters.

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